fsl/fman: implement several errata workarounds

Implemented workarounds for the following dTSEC Erratum:
A002, A004, A0012, A0014, A004839 on several operations
that involve MAC CFG register changes: adjust link,
rx pause frames, modify MAC address.

Signed-off-by: Florinel Iordache <florinel.iordache@nxp.com>
Acked-by: Madalin Bucur <madalin.bucur@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>